JP7156938B2 - Bidirectional inverter and power storage system provided with the bidirectional inverter - Google Patents

Description

The present invention relates to a bidirectional inverter, particularly to a bidirectional inverter to which an ARCP (Auxiliary Resonant Commutated Pole) method is applied, and to a power storage system including the bidirectional inverter.

In the technical field of power storage systems, there have been conventional examples of using low-cost electricity to charge batteries at midnight and discharge the charged electricity during the daytime to reduce the amount of electricity purchased from electric power companies. Are known.

FIG. 3 shows a circuit diagram of a conventional general power storage system. In FIG. 3, 1 is an AC system, 2 is a self-sustaining output, S1, S2, S3, S4, S5, and S6 are switches, 3 is a noise filter, C0 is an interphase capacitor, L1 and L2 are choke coils, and 4 is bidirectional. An inverter, Q1, Q2, Q3, and Q4 are main switching elements forming a bidirectional inverter 4, 5 is a bidirectional DC/DC converter, C1 is a first smoothing capacitor, and Q5 and Q6 are a bidirectional DC/DC converter 5. A main switching element, L3 is a choke coil, C2 is a second smoothing capacitor, and BT is a storage battery.

During the charging operation, the switches S1 to S4 are turned on, and the switches S5 and S6 are turned off (the stand-alone output 2 and the noise filter 3 are connected in parallel to the AC system 1), and the AC system 1 is converted into a boosted DC voltage by a bi-directional inverter 4 . Then, the DC voltage is stepped down by the bidirectional DC/DC converter 5 to the DC voltage required by the storage battery BT, and the storage battery BT is charged.

During the discharge operation, the switches S1 to S4 are turned on, the switches S5 and S6 are turned off, and the bidirectional DC/DC converter 5 boosts the voltage of the storage battery BT. Then, the direct current is converted into a stepped-down alternating current by the bidirectional inverter 4 and discharged to the alternating current system 1 and the isolated output 2 .

When the AC system 1 has a power failure, the switches S1 to S4 are turned off, and the switches S5 and S6 are turned on (the AC system 1 is separated from the noise filter 3 and the isolated output 2, and the isolated output 2 is connected to the noise filter 3 ), and an alternating current is output from the storage battery BT to the self-sustained output 2 in the same manner as during the discharge operation. The self-sustained output 2 is connected to home electric appliances to be preferentially used in the event of a power failure.

By the way, the current situation is that the power storage system is expensive to be widely used in general households (especially, the storage battery BT is pushing up the price), and it is difficult to purchase it easily.

In the general market, there is a demand to reduce the price even if the storage battery capacity is sacrificed, and in order to meet this demand, it is necessary to reduce the number of series storage batteries BT and develop a product with a lower price. is coming.

However, if the number of series storage batteries BT is reduced, the storage battery voltage will drop, and the step-up/step-down ratio of the bidirectional DC/DC converter 5 (step-down ratio during charging, step-up ratio during discharging) will increase. is a problem.

As a countermeasure against efficiency deterioration, an ARCP circuit for improving the efficiency of a bidirectional DC/DC converter is proposed in a paper on a highly efficient bidirectional isolated DC/DC converter (see Non-Patent Document 1).

FIG. 4 shows an ARCP circuit additionally applied to the bidirectional DC/DC converter 5 in the power storage system of FIG.

In FIG. 4, 6' is an ARCP circuit, 6a' is a commutation control circuit, 6b' is a rectifier circuit, L4 is a resonance coil, Q7 and Q8 are auxiliary switching elements, T0 is a charge/discharge transformer, D1 and D2 are Rectifying diodes, D3 and D4 are backflow prevention diodes, and C3 and C4 are resonance capacitors. In FIG. 4, the same reference numerals as those used in FIG. 3 denote the same components, and detailed description thereof will be omitted.

An ARCP circuit 6' is additionally applied to the bidirectional DC/DC converter 5. FIG. The ARCP circuit 6' has a commutation control circuit 6a' and a rectifier circuit 6b'. The commutation control circuit 6a' has a resonance coil L4, auxiliary switching elements Q7 and Q8, resonance capacitors C3 and C4, a transformer T0 for charging and discharging, and diodes D3 and D4 for preventing backflow. The rectifier circuit 6b' is composed of rectifier diodes D1 and D2.

The functions of the ARCP circuit 6' are as follows.

A series circuit of a choke coil L3 and a main switching element Q6 is connected between both terminals of the second smoothing capacitor C2. A series circuit of a diode and a first smoothing capacitor C1 is connected, which forms the function of a boost chopper in the case of discharge mode.

The function of the boost chopper is exhibited by switching the main switching element Q6 on the low side. The switching element Q6 can be turned on by a soft switching method, and the conversion efficiency can be improved.

A series circuit of the high-side main switching element Q5 and the antiparallel-connected parasitic diode in the low-side main switching element Q6 is connected between both terminals of the first smoothing capacitor C1. A series circuit of a coil L3 and a second smoothing capacitor C2 is connected, which forms the function of a step-down chopper in the case of charging mode.

The function of the step-down chopper is exhibited by switching the main switching element Q5 on the high side. The side main switching element Q5 can be turned on by a soft switching method, and the conversion efficiency can be improved.

In the circuit disclosed in the above paper, the diodes D3 and D4 for preventing backflow are not inserted in series with the auxiliary switching elements Q7 and Q8, but in reality the reverse voltage generated from the transformer T0 for both charging and discharging is The diodes D3 and D4 for preventing backflow are indispensable in order to prevent the backflow caused by the current.

By the way, even if the ARCP circuit is adopted as described above, the step-up/step-down ratio is still as high as about 5 times in consideration of the price reduction of the storage battery BT, and further improvement of the conversion efficiency is an issue.

Therefore, in order to achieve further improvement, the applicant proposed an electricity storage system as shown in FIG. 5 (a patent application has been filed for the main part of the system). This corresponds to replacing the ARCP circuit 6' in the bidirectional DC/DC converter 5 in FIG. 5, the same reference numerals as those used in FIGS. 3 and 4 indicate the same components, and detailed description thereof will be omitted.

In FIG. 5, the charging/discharging transformer T0 in the commutation control circuit 6a' of FIG. 4 is separated into a high-side transformer T1 for charging and a low-side transformer T2 for discharging. In accordance with this separation of the transformer, the rectifier circuit 6b has rectifier diodes D5 and D6 added to the rectifier diodes D1 and D2 in the case of FIG.

During charging, the high-side auxiliary switching element Q7 switches and drives the high-side transformer T1 for charging. Since there is no voltage in the high-side transformer T1 for charging, the switching of the high-side auxiliary switching element Q7 does not generate a voltage in the low-side transformer T2 for discharging. The diode D4 for backflow prevention in the case of 4 is not necessary.

During discharging, the low-side auxiliary switching element Q8 switches to drive the low-side discharging transformer T2. Since it does not exist in the low-side transformer T2 for discharging, no voltage is generated in the high-side transformer T1 for charging by the switching of the low-side auxiliary switching element Q8. The diode D3 for backflow prevention in the case of 4 is not necessary.

As described above, since it is not necessary to insert the diodes (D3, D4) for preventing backflow, the power lost by the diodes for preventing backflow is eliminated, and the conversion efficiency can be improved.

A brief description has been given above of how the ARCP circuit 6 was additionally applied to the bidirectional DC/DC converter 5 of the power storage system including the bidirectional inverter 4 and the bidirectional DC/DC converter 5 .

"High Efficiency, Bi-Directional Isolated DCDC Converter", [online], 2002, Pony Electric Co., Ltd., [searched November 12, 2018], Internet <URL: http://pony-e.jp/High_efficiency_bi -directional_insulated_DCDCconverter.pdf>

A case where the ARCP circuit 6 is applied to the bidirectional inverter 4 instead of the bidirectional DC/DC converter 5 will be described below with reference to FIG. The power storage system shown in FIG. 6 is a configuration example for clarifying the subject of the present invention, and should not be regarded as conventional technology.

FIG. 6 is a circuit diagram showing an electricity storage system that has been studied with the expectation of improving the conversion efficiency based on the electricity storage system of FIG. 6, the same reference numerals as those used in FIGS. 3, 4, and 5 indicate the same components, and detailed description thereof will be omitted.

The power storage system in FIG. 6 corresponds to the power storage system in FIG. 3 in which the ARCP circuit is additionally applied to the bidirectional inverter 4 (again, the ARCP circuit is applied to the bidirectional DC/DC converter 5). is applied to the bidirectional inverter 4 instead of ).

6, the bidirectional DC/DC converter 5 shown as one block and indicated by reference numeral 5 does not show its internal configuration, but as in FIG. It comprises switching elements Q5 and Q6, a choke coil L3, and first and second smoothing capacitors C1 and C2. For convenience of explanation, the first smoothing capacitor C1 is shown protruding outside the block showing the bidirectional DC/DC converter 5. As shown in FIG.

In FIG. 6, the portion corresponding to the bidirectional inverter 4 in FIG. 3 is composed of two bidirectional inverter sections, ie, a first bidirectional inverter section 4a and a second bidirectional inverter section 4b.

Next, the components of the first and second bidirectional inverter sections 4a and 4b will be described with reference to the components of the ARCP circuit 6 (transformer isolation system) of the bidirectional DC/DC converter 5 in FIG.

As explained with the circuit configuration of FIG. It has a pressure-lowering function in the direction toward the side of On the other hand, the bidirectional DC/DC converter 5 including the ARCP circuit 6 shown in FIG. It has a boosting function in the direction from to the AC system 1 side. That is, in the bidirectional inverter 4 and the bidirectional DC/DC converter 5 including the ARCP circuit 6, the current flow direction is symmetrical (reverse) with respect to the directionality of the step-up/step-down.

Taking this into consideration, the arrangement order of the components of the first and second bidirectional inverter sections 4a and 4b in FIG. 6 is the reverse of the arrangement order of the components of the bidirectional DC/DC converter 5 in FIG. It is good if there is a directional relationship.

In FIG. 6, the ARCP circuit 6 in the first bidirectional inverter section 4a has a commutation control circuit 6a and a rectification circuit 6b, and the ARCP circuit 7 in the second bidirectional inverter section 4b has a commutation control circuit 7a and a rectification circuit 6b. It has a circuit 7b.

Commutation control circuits 6a and 7a include resonance coils L5 and L6, high-side auxiliary switching elements Q9 and Q11, primary windings of high-side charging transformers T3 and T5, and low-side discharging transformers T4 and T6. has a primary winding and low-side auxiliary switching elements Q10 and Q12. The commutation control circuits 6a and 7a are not connected to the backflow prevention diodes D3 and D4 in FIG.

In the first bidirectional inverter section 4a, the high-side choke coil L1 on the noise filter 3 side corresponds to the choke coil L3 positioned on the storage battery BT side in FIG. In the second bidirectional inverter section 4b, the low-side choke coil L2 on the noise filter 3 side corresponds to the choke coil L3 in FIG.

Similarly, the high-side main switching elements Q1 and Q3 correspond to the high-side main switching element Q5 in FIG. 5, and the low-side main switching elements Q2 and Q4 correspond to the low-side main switching element Q6 in FIG. Resonance coils L5 and L6 correspond to resonance coil L4 in FIG.

The auxiliary switching elements Q9 and Q11 correspond to the high side auxiliary switching element Q7 in the commutation control circuit 6a of FIG. 5, and the auxiliary switching elements Q10 and Q12 correspond to the low side auxiliary switching element Q8 of FIG. High-side transformers T3 and T5 for charging correspond to the high-side charging transformer T1 in the commutation control circuit 6a of FIG. It corresponds to the low-side transformer T2 for discharge. High-side resonance capacitors C5 and C7 correspond to resonance capacitor C3 in FIG. 5, and low-side resonance capacitors C6 and C8 correspond to resonance capacitor C4 in FIG.

In FIG. 6, the rectifier circuit 6b in the first bidirectional inverter section 4a is composed of rectifier diodes D7, D8, D9 and D10, and the rectifier circuit 6b in the second bidirectional inverter section 4b is composed of rectifier diodes D11, D12 and D13. , D14.

The rectifier diodes D7, D8, D9 and D10 and the rectifier diodes D11, D12, D13 and D14 in FIG. 6 correspond to the rectifier diodes D1, D2, D5 and D6 in FIG.

However, in the power storage system shown in FIG. 6, the bidirectional inverter 4 does not perform step-up conversion or step-down conversion between DC voltages like the bidirectional DC/DC converter 5 does. Since the AC system 1 side or the isolated output 2 side of the bidirectional inverter 4 becomes an AC voltage, the duty of the main switching elements Q1, Q2, Q3, Q4 varies in a wide range. That is, the duty varies greatly from the minimum duty (maximum voltage of the sine wave) to the maximum duty (zero voltage of the sine wave).

Therefore, if the ARCP circuit is simply applied to the bidirectional inverter 4, the mode of operation will deviate from the resonance condition due to the high-side/low-side auxiliary switching elements Q9, Q10 or Q11, Q12. As a result, it becomes difficult to perform the soft switching as expected, and the operation of the bidirectional inverter 4 becomes unstable.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and aims at stabilizing the operation and improving the conversion efficiency of a bidirectional inverter to which an ARCP circuit is applied.

The present invention solves the above problems by taking the following measures.

A bidirectional inverter according to the present invention is
a first bidirectional inverter section and a second bidirectional inverter section provided between a high side line and a low side line that constitute a pair of power supply lines;
The first bidirectional inverter section has a series circuit of a high-side main switching element and a low-side main switching element and a first ARCP circuit,
The second bidirectional inverter section has a series circuit of a high-side main switching element and a low-side main switching element and a second ARCP circuit,
each of the first and second ARCP circuits includes a high-side auxiliary switching element corresponding to the high-side main switching element and a low-side auxiliary switching element corresponding to the low-side main switching element;
The high-side auxiliary switching element is turned on before the high-side main switching element is turned on to commutate current, thereby performing soft switching of the high-side main switching element and the low-side auxiliary switching element. is turned on before the low-side main switching element is turned on to commutate current, thereby performing soft switching of the low-side main switching element;
The switching control circuit for the high-side and low-side auxiliary switching elements is configured to stop the operation of each of the auxiliary switching elements before the duty of the high-side and low-side main switching elements reaches a predetermined limit duty state. It is characterized by being

In addition, the power storage system according to the present invention is
The bidirectional inverter having the above configuration and the bidirectional DC/DC converter are connected in series between the AC system and the storage battery,
a smoothing capacitor is connected between the high side line and the low side line connecting the bidirectional inverter and the bidirectional DC/DC converter;
a common connection point between the high-side main switching element and the low-side main switching element in the first bidirectional inverter section is connected to the high-side choke coil on the AC system side;
A common connection point between the high-side main switching element and the low-side main switching element in the second bidirectional inverter section is connected to a low-side choke coil on the AC system side.

According to the configuration of the present invention, an ARCP circuit is additionally applied to the bidirectional inverter. In this case, a first bidirectional inverter section and a first ARCP circuit are provided for the AC positive half cycle period, and a second bidirectional inverter section and a second ARCP circuit are provided for the negative half cycle period. and turning on each of the high-side and low-side auxiliary switching elements before turning on the respective high-side main switching elements and low-side main switching elements in both the first and second bidirectional inverter sections. Soft switching can be performed by commutating the current.

However, a bidirectional inverter is connected between an AC system and a DC system, and unlike a bidirectional DC/DC converter that is connected between DC systems, the duty of the main switching element changes greatly. . Therefore, in the bidirectional inverter to which the ARCP circuit is additionally applied, the soft switching mode of the main switching element deviates from the resonance condition of the auxiliary switching element, and the soft switching becomes unstable.

However, in the present invention, in the switching control of the high-side and low-side auxiliary switching elements in the ARCP circuit, each auxiliary switching element is controlled before the duty of the high-side and low-side main switching elements largely changes and reaches a predetermined limit duty state. It stops the operation of the device.

As a result, in both the first bidirectional inverter section and the second bidirectional inverter section, the soft switching of the main switching elements is stabilized, and the conversion efficiency of the bidirectional inverter can be improved.

The bidirectional inverter of the present invention having the above configuration has the following preferred aspects.

the first and second ARCP circuits each have a commutation control circuit and a rectification circuit;
In the commutation control circuit, a series circuit of the high-side auxiliary switching element, the primary winding of a transformer, and the low-side auxiliary switching element is connected between the high-side line and the low-side line. A common connection point of the low-side main switching elements and the primary winding of the transformer are connected via a resonance coil, and high-side and low-side main switching elements are connected between both terminals constituting current paths of the high-side and low-side main switching elements, respectively. A low-side resonant capacitor is connected in parallel,
The rectifier circuit may be configured to supply a current induced in a secondary winding of the transformer in a direction from the high side line to the low side line.

In this case, stabilization of soft switching of the main switching element and improvement of conversion efficiency of the bidirectional inverter become more effective.

Further, the transformer includes a high-side transformer having a primary winding connected to the high-side auxiliary switching element and a low-side transformer having a primary winding connected to the low-side auxiliary switching element, There is a mode in which the high-side transformer and the low-side transformer are separated from each other without being substantially magnetically coupled.

In this case, the transformer for magnetic coupling between the commutation control circuit and the rectifier circuit is separated into a discharging transformer and a charging transformer. Energizing the primary winding will not cause a back EMF in the high side primary winding, nor will energizing the high side primary winding cause a back EMF in the low side primary winding. As a result, it is no longer necessary to insert backflow prevention diodes in both the high-side and low-side portions of the ARCP circuit as in the conventional example, and it is possible to save the power consumed by the backflow prevention diodes. Become.

According to the present invention, it is possible to stabilize the operation and improve the conversion efficiency in the bidirectional inverter to which the ARCP circuit is applied.

1 is a circuit diagram showing the configuration of a power storage system according to an embodiment of the present invention; FIG. Explanatory diagram of switching control of the storage system in the embodiment of the present invention Circuit diagram showing the configuration of a conventional power storage system A circuit diagram showing the configuration of an electricity storage system in another conventional example A circuit diagram showing the configuration of a power storage system improved from the conventional example shown in FIG. Circuit diagram showing a configuration example of a power storage system equipped with a bidirectional inverter using an ARCP circuit

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the bidirectional inverter of the present invention configured as described above and an electric storage system equipped with the bidirectional inverter will be described in detail at the level of specific examples.

As shown in FIG. 1, a bidirectional inverter 4 and a bidirectional DC/DC converter 5 are connected in series between an AC system (commercial power system) 1 and a storage battery BT. A first smoothing capacitor C1 is connected between the high-side line LH and the low-side line LL, which are power supply lines of the bidirectional DC/DC converter 5 . Although the first smoothing capacitor C1 is one of the components of the bidirectional DC/DC converter 5, it is shown outside the block showing the bidirectional DC/DC converter 5 for convenience of explanation.

A noise filter 3 is connected to the AC system 1 through a pair of high-side and low-side switches S1 and S2, and to the independent output 2 through a pair of high-side and low-side switches S5 and S6. A noise filter 3 is connected. The AC system 1 and the isolated output 2 are connected in parallel via a pair of high-side and low-side switches S3 and S4.

The bidirectional inverter 4 is composed of a first bidirectional inverter section 4a on the front stage side and a second bidirectional inverter section 4b on the rear stage side.

An interphase capacitor C0 is connected between the output terminals of the noise filter 3, and a high side line LH on the output side of the noise filter 3 is connected to a first bidirectional inverter section in the bidirectional inverter 4 via a high side choke coil L1. 4a is connected, and the second bidirectional inverter section 4b in the bidirectional inverter 4 is connected to the low side line LL on the output side of the noise filter 3 via the low side choke coil L2.

The first bidirectional inverter section 4 a is composed of a series circuit of a high-side main switching element Q 1 and a low-side main switching element Q 2 and a first ARCP circuit 6 . A series circuit of the main switching elements Q1 and Q2 is connected between a high side line LH and a low side line LL which are power supply lines with the first smoothing capacitor C1 in the bidirectional DC/DC converter 5 interposed therebetween.

The first ARCP circuit 6 is composed of a commutation control circuit 6a and a rectifier circuit 6b.
The commutation control circuit 6a includes a series circuit of a high-side auxiliary switching element Q9, the primary windings of transformers (T3 and T4), and a low-side auxiliary switching element Q10, a resonance coil L5, and a high-side resonance capacitor C5. It is composed of a low-side resonance capacitor C6.

The transformers (T3, T4) connected between the high-side auxiliary switching element Q9 and the low-side auxiliary switching element Q10 are separated into a high-side transformer T3 and a low-side transformer T4. That is, the primary winding of the high-side transformer T3 and the primary winding of the low-side transformer T4 are connected in series, and the series circuit is connected between the auxiliary switching element Q9 and the auxiliary switching element Q10.

Resonance occurs between a common connection point N1 between the primary winding of the high-side transformer T3 and the primary winding of the low-side transformer T4 and a common connection point N2 between the high-side main switching element Q1 and the low-side main switching element Q2. coil L5 is connected. Furthermore, a high-side resonance capacitor C5 is connected between both terminals forming the current path of the high-side main switching element Q1, and a low-side resonance capacitor C5 is connected between both terminals forming the current path of the low-side main switching element Q2. A capacitor C6 is connected.

As described above, the common connection point N2 of the main switching elements Q1 and Q2, the resonance coil L5, and the resonance capacitors C5 and C6 is connected to the high-side choke coil L1 on the AC system 1 side.

The rectifier circuit 6b in the first ARCP circuit 6 has four rectifier diodes D7, D8, D9 and D10. The rectifier diode D7 has its anode connected to one end of the secondary winding of the high-side transformer T3, and its cathode connected to the high-side line LH.

The rectifier diode D8 has its anode connected to the other end of the secondary winding of the high-side transformer T3, and its cathode connected to the high-side line LH. The middle tap of the secondary winding of the high side transformer T3 is connected to the low side line LL.

The rectifier diode D9 has its anode connected to one end of the secondary winding of the low-side transformer T4, and its cathode connected to the high-side line LH. The rectifier diode D10 has its anode connected to the other end of the secondary winding of the high-side transformer T5, and its cathode connected to the high-side line LH. The middle tap of the secondary winding of the low-side transformer T4 is connected to the low-side line LL.

As described above, the rectifier circuit 6b causes the current induced in the secondary windings of the transformers (T3, T4) to flow in one direction from the high side line LH to the low side line LL to the first smoothing capacitor C1. configured to supply

The second bidirectional inverter section 4 b is composed of a series circuit of a high-side main switching element Q 3 and a low-side main switching element Q 4 and a second ARCP circuit 7 . A series circuit of the main switching elements Q3 and Q4 is connected between the high side line LH and the low side line LL.

The second ARCP circuit 7 is composed of a commutation control circuit 7a and a rectifier circuit 7b. The commutation control circuit 7a includes a series circuit of a high-side auxiliary switching element Q11, the primary windings of transformers (T5 and T6), and a low-side auxiliary switching element Q12, a resonance coil L6, and a high-side resonance capacitor C7. It is composed of a low-side resonance capacitor C8.

The transformers (T5, T6) connected between the high-side auxiliary switching element Q11 and the low-side auxiliary switching element Q12 are separated into a high-side transformer T5 and a low-side transformer T6. That is, the primary winding of the high-side transformer T5 and the primary winding of the low-side transformer T6 are connected in series, and the series circuit is connected between the auxiliary switching element Q11 and the auxiliary switching element Q12.

Resonance occurs between a common connection point N3 between the primary winding of the high-side transformer T5 and the primary winding of the low-side transformer T6 and a common connection point N4 between the high-side main switching element Q3 and the low-side main switching element Q4. coil L6 is connected. Furthermore, a high-side resonance capacitor C7 is connected between both terminals forming the current path of the high-side main switching element Q3, and a low-side resonance capacitor C7 is connected between both terminals forming the current path of the low-side main switching element Q4. A capacitor C8 is connected.

As described above, the common connection point N4 of the main switching elements Q3, Q4, the resonance coil L6, and the resonance capacitors C7, C8 is connected to the low-side choke coil L2 on the AC system 1 side.

The rectifier circuit 7b in the second ARCP circuit 7 has four rectifier diodes D11, D12, D13 and D14. The rectifier diode D11 has its anode connected to one end of the secondary winding of the high-side transformer T5, and its cathode connected to the high-side line LH. The rectifier diode D12 has its anode connected to the other end of the secondary winding of the high-side transformer T5, and its cathode connected to the high-side line LH. The middle tap of the secondary winding of the high side transformer T5 is connected to the low side line LL.

The rectifier diode D13 has its anode connected to one end of the secondary winding of the low-side transformer T6, and its cathode connected to the high-side line LH. The rectifier diode D14 has its anode connected to the other end of the secondary winding of the low-side transformer T6, and its cathode connected to the high-side line LH. The center tap of the secondary winding of the low-side transformer T6 is connected to the low-side line LL.

As described above, the rectifier circuit 7b causes the current induced in the secondary windings of the transformers (T5, T6) to flow in one direction from the high side line LH to the low side line LL to the first smoothing capacitor C1. configured to supply

In the present invention, the switching control circuit 8 for the high-side auxiliary switching elements Q9 and Q11 and the low-side auxiliary switching elements Q10 and Q12 causes the duty of the high-side main switching elements Q1 and Q3 to reach a predetermined limit duty state. before the operation of the high-side auxiliary switching elements Q9 and Q11 is stopped, and before the duty of the low-side main switching elements Q2 and Q4 reaches a predetermined limit duty state, the low-side auxiliary switching elements Q10 and Q12 are operated. is configured to stop

The duty state of the predetermined limit when stopping the operation of the auxiliary switching elements Q9, Q10, Q11, Q12 may be determined according to the circuit constant of each component in the individual power storage system.

FIG. 2 shows an example of a predetermined limit duty. For example, when the resonance conditions of the auxiliary switching elements Q9, Q10, Q11, and Q12 are not met at the lower limit of the duty of 15% and the upper limit of the duty of 80%, the switching control circuit 8 controls the main switching element with respect to the input AC voltage. The duties of Q1, Q2, Q3 and Q4 are monitored, before reaching the first and second regions reg1 and reg2 where the duty is 15% or less, for example, and before reaching the third and fourth region reg3 where the duty is 80% or more. , reg4, the operation of the auxiliary switching elements Q9, Q10, Q11, Q12 is stopped.

(1) Assume that the main switching elements Q1, Q2, Q3, Q4 and the auxiliary switching elements Q9, Q10, Q11, Q12 are in the OFF state in a certain phase. This is the steady state prior to commutation operation. Before commutation, no current flows through the commutation control circuits 6a and 7a, and no current flows through the rectifier circuits 6b and 7b. In this state, the phase-to-phase capacitor C0→high-side choke coil L1→common connection point N2→antiparallel-connected parasitic diode of the high-side main switching element Q1→high-side line LH→first smoothing capacitor C1→low-side line LL →Antiparallel-connected parasitic diode of the low-side main switching element Q4→Common connection point N4→Interphase capacitor C0.

(2) In the next phase, the low-side auxiliary switching element Q10 and the high-side auxiliary switching element Q11 are turned on. As a result, due to commutation, the path from the common connection point N2→the resonance coil L5→the primary winding of the low-side transformer T4→the low-side auxiliary switching element Q10 to the high-side auxiliary switching element Q11→the high-side transformer T5 primary. A path of winding→resonance coil L6→common connection point N4 is formed. Rectification by the voltage induced in the secondary winding of the transformer T4 on the low side through the rectifier diodes D9 and D10 through the high side line LH and by the voltage induced in the secondary winding of the transformer T5 on the high side The first smoothing capacitor C1 is charged from the diodes D11 and D12 via the high side line LH (charging by the rectifier circuits 6b and 7b).

(3) In the next phase, further commutation activates the low-side resonant capacitor C6 and the high-side resonant capacitor C7, resulting in resonant operation. Charging of the first smoothing capacitor C1 by the rectifier circuits 6b and 7b is continued.

(4) In the next phase, when the voltage across the low-side resonance capacitor C6 becomes 0 level, the low-side main switching element Q2 is turned on. Further, when the voltage across the high-side resonance capacitor C7 becomes 0 level, the high-side main switching element Q3 is turned on. The turn-on of the main switching elements Q2 and Q3 utilizes soft switching (zero voltage switching (ZVS)) due to a high frequency resonance phenomenon, and switching loss is reduced.

When the low-side main switching element Q2 is turned on, the current flowing through the resonance coil L5 gradually decreases and transitions to a current centering on the low-side main switching element Q2. Similarly, when the high-side main switching element Q3 is turned on, the current flowing through the resonance coil L6 gradually decreases and transitions to a current centering on the high-side main switching element Q3. Charging of the first smoothing capacitor C1 by the rectifier circuits 6b and 7b is continued.

(5) In the next phase, the current in the resonance coil L5 disappears and the low-side auxiliary switching element Q10 turns off, and the current in the resonance coil L6 disappears and the high-side auxiliary switching element Q11 turns off. The turn-off of the auxiliary switching elements Q10 and Q11 utilizes soft switching (zero current switching (ZCS)) to reduce switching loss. In this steady state, the current flows as follows: interphase capacitor C0→high side choke coil L1→common connection point N2→low side main switching element Q2→low side line LL→first smoothing capacitor C1→high side line LH→high side The current flows only along the main switching element Q3→common connection point N4→low-side choke coil L2→interphase capacitor C0. Therefore, the high-side choke coil L1 and the low-side choke coil L2 accumulate energy. Since no current flows through the primary winding of the low-side transformer T4 and the primary winding of the high-side transformer T5, no current flows through the rectifier circuits 6b and 7b.

(6) In the next phase, the low-side main switching element Q2 and the high-side main switching element Q3 are turned off. From that moment on, the current is commutated to the resonance capacitors C6, C7 and the resonance capacitors C6, C7 are charged. While the voltage across the main switching elements Q2 and Q3 rises slowly, the current is quickly transferred to the resonance capacitors C6 and C7, resulting in almost no switching loss.

(7) In the next phase, the main switching elements Q1, Q2, Q3, Q4 and the auxiliary switching elements Q9, Q10, Q11, Q12 are in the off state, and the high-side choke coil L1 and the low-side choke coil L2 are energized. interphase capacitor C0 → choke coil L2 on the low side → common connection point N4 → parasitic diode of anti-parallel connection of the main switching element Q3 on the high side → high side line LH → first smoothing capacitor C1 → low side line LL → A current flows through the path of the antiparallel-connected parasitic diode of the low-side main switching element Q2→the common connection point N2→the high-side choke coil L1→the interphase capacitor C0. This is the steady state prior to commutation operation. Before commutation, no current flows through the commutation control circuits 6a and 7a, and no current flows through the rectifier circuits 6b and 7b.

(8) In the next phase, the low-side auxiliary switching element Q12 and the high-side auxiliary switching element Q9 are turned on. As a result, due to commutation, the path from the common connection point N4→the resonance coil L6→the primary winding of the low-side transformer T6→the low-side auxiliary switching element Q12 to the high-side auxiliary switching element Q9→the high-side transformer T3 primary. A path of winding→resonance coil L5→common connection point N2 is formed. Rectification by the voltage induced in the secondary winding of the transformer T6 on the low side, from the rectifier diodes D13 and D14 via the high side line LH, and by the voltage induced in the secondary winding of the transformer T3 on the high side The first smoothing capacitor C1 is charged from the diodes D7 and D8 through the high side line LH (charging by the rectifier circuits 6b and 7b).

(9) In the next phase, further commutation activates the low-side resonant capacitor C8 and the high-side resonant capacitor C5, resulting in resonant operation. Charging of the first smoothing capacitor C1 by the rectifier circuits 6b and 7b is continued.

(10) In the next phase, when the voltage across the low-side resonance capacitor C8 becomes 0 level, the low-side main switching element Q4 is turned on. Further, when the voltage across the high-side resonance capacitor C5 becomes 0 level, the high-side main switching element Q1 is turned on. The turn-on of the main switching elements Q4 and Q1 utilizes soft switching (zero voltage switching (ZVS)) due to a high frequency resonance phenomenon, and switching loss is reduced.

When the low-side main switching element Q4 is turned on, the current flowing through the resonance coil L6 gradually decreases and transitions to a current centering on the low-side main switching element Q4. Similarly, when the high-side main switching element Q1 is turned on, the current flowing through the resonance coil L5 gradually decreases and transitions to a current centering on the high-side main switching element Q1. Charging of the first smoothing capacitor C1 by the rectifier circuits 6b and 7b is continued.

(11) In the next phase, the resonance coil L6 loses current, turning off the low-side auxiliary switching element Q12, and the resonance coil L5 loses current, turning off the high-side auxiliary switching element Q9. The turn-off of the auxiliary switching elements Q12 and Q9 utilizes soft switching (zero current switching (ZCS)) to reduce switching loss. In this steady state, the current flows as follows: interphase capacitor C0→low-side choke coil L2→common connection point N4→low-side main switching element Q4→low-side line LL→first smoothing capacitor C1→high-side line LH→high-side main switching element The current flows only through the switching element Q1→common connection point N2→high-side choke coil L1→interphase capacitor C0. Therefore, the low-side choke coil L2 and the high-side choke coil L1 accumulate energy. Since no current flows through the primary winding of the transformer T6 on the low side and the primary winding of the transformer T3 on the high side, no current flows through the rectifier circuits 6b and 7b.

(12) In the next phase, the low-side main switching element Q4 and the high-side main switching element Q1 are turned off. From that moment on, the current is commutated to the resonance capacitors C8 and C5, charging the resonance capacitors C8 and C5. Although the voltage across the main switching elements Q4 and Q1 rises slowly, the current is quickly transferred to the resonance capacitors C8 and C5, so that almost no switching loss occurs.

In the power storage system of the embodiment configured and operated as described above, the switching control circuit 8 monitors the duty of the main switching elements Q1, Q2, Q3, Q4 with respect to the input AC voltage, and the duty is 15% or less (one example). and before reaching the third and fourth regions reg3 and reg4 where the duty is 80% or more (one example), the auxiliary switching elements Q9, Q10, Q11 , Q12 are stopped. As a result, in both the first bidirectional inverter section 4a and the second bidirectional inverter section 4b, the soft switching operation of the main switching elements Q1, Q2 or Q3, Q4 is stabilized, and the conversion efficiency is improved. be able to. As a result, the charge/discharge operation of the power storage system can be made highly efficient.

Although the specific configuration of the bidirectional DC/DC converter 5 is not particularly mentioned in the above embodiment, it may be a circuit configuration without an ARCP circuit as shown in FIG. A circuit configuration including an ARCP circuit having a transformer for both charging and discharging, or a circuit configuration in which a high-side transformer for charging and a low-side transformer for discharging are separated as shown in FIG. 5 may be used.

INDUSTRIAL APPLICABILITY The present invention is useful as a technique for improving the conversion efficiency of a bidirectional inverter to which an ARCP circuit is applied.

1 AC system 4 Bidirectional inverter 4a First bidirectional inverter unit 4b Second bidirectional inverter unit 5 Bidirectional DC/DC converter 6 First ARCP circuit 7 Second ARCP circuit 6a, 7a Commutation control circuit 6b , 7b rectifier circuit 8 switching control circuit BT storage battery C2 smoothing capacitor (second smoothing capacitor)
C5, C7 High side resonance capacitor C6, C8 Low side resonance capacitor L5, L6 Resonance coil L1 High side choke coil L2 Low side choke coil LH High side line LL Low side line N2, N4 Common connection point Q1, Q3 High side main switching element Q2, Q4 Low side main switching element Q9, Q11 High side auxiliary switching element Q10, Q12 Low side auxiliary switching element T3, T5 High side transformer T4, T6 Low side transformer

Claims (4)

a first bidirectional inverter section and a second bidirectional inverter section provided between a high side line and a low side line that constitute a pair of power supply lines;
The first bidirectional inverter section has a series circuit of a high-side main switching element and a low-side main switching element and a first ARCP circuit,
The second bidirectional inverter section has a series circuit of a high-side main switching element and a low-side main switching element and a second ARCP circuit,
each of the first and second ARCP circuits includes a high-side auxiliary switching element corresponding to the high-side main switching element and a low-side auxiliary switching element corresponding to the low-side main switching element;
The high-side auxiliary switching element is turned on before the high-side main switching element is turned on to commutate current, thereby performing soft switching of the high-side main switching element and the low-side auxiliary switching element. is turned on before the low-side main switching element is turned on to commutate current to perform soft switching of the low-side main switching element;
The switching control circuit for the high-side and low-side auxiliary switching elements controls the switching before the duty of the high-side and low-side main switching elements reaches a predetermined limit duty state that deviates from the resonance condition in each ARCP circuit. A bidirectional inverter, characterized in that it is configured to stop the operation of each auxiliary switching element. the first and second ARCP circuits each have a commutation control circuit and a rectification circuit;
In the commutation control circuit, a series circuit of the high-side auxiliary switching element, the primary winding of a transformer, and the low-side auxiliary switching element is connected between the high-side line and the low-side line. A common connection point of the low-side main switching elements and the primary winding of the transformer are connected via a resonance coil, and high-side and low-side main switching elements are connected between both terminals constituting current paths of the high-side and low-side main switching elements, respectively. A low-side resonant capacitor is connected in parallel,
2. The bidirectional inverter according to claim 1, wherein said rectifier circuit is configured to supply current induced in a secondary winding of said transformer in one direction toward said high side line. The transformer includes a high-side transformer having a primary winding connected to the high-side auxiliary switching element and a low-side transformer having a primary winding connected to the low-side auxiliary switching element, and the low-side transformer are separated from each other without substantial magnetic coupling ,
a resonance coil between a common connection point between the primary winding of the high-side transformer and the primary winding of the low-side transformer and a common connection point between the high-side main switching element and the low-side main switching element; 3. The bi-directional inverter according to claim 2, wherein the is connected to . The bidirectional inverter according to any one of claims 1 to 3 and the bidirectional DC/DC converter are connected in series between the AC system and the storage battery,
a smoothing capacitor is connected between the high side line and the low side line connecting the bidirectional inverter and the bidirectional DC/DC converter;
a common connection point between the high-side main switching element and the low-side main switching element in the first bidirectional inverter section is connected to the high-side choke coil on the AC system side;
A power storage system in which a common connection point between the high-side main switching element and the low-side main switching element in the second bidirectional inverter section is connected to a low-side choke coil on the AC system side.

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